This invention relates to a moving picture coding experts group (MPEG) data processing apparatus for processing MPEG video data at a high speed.
As is well known in the art, MPEG is a picture information compressive coding technique for a digital video signal. MPEG codes the digital video signal into a coded digital video signal which is called MPEG video data. The MPEG video data are classified into three types, namely, intra coded picture data, predictive coded picture data, and bidirectionally predictive picture data. Each of the intra coded picture data indicates an intra coded picture which is called an I-picture for short. Each of the predictive coded picture data indicates a predictive coded picture which is called a P-picture for short. Each of the bidirectionally predictive picture data indicates a bidirectionally predictive picture which is called a B-picture for short.
The I-picture datum is generated without use of interframe prediction. The P-picture datum is generated by carrying out prediction on a previous I-picture datum or a previous P-picture datum. The B-picture datum is generated by carrying out prediction on, two fore and aft picture data each of which is the I-picture datum or the P-picture datum.
In picture reproduction, in a case of carrying out a fast feed or the like, in order to processing the MPEG video data at a high-speed, a method comprising the steps of decoding only the I-picture data and the P-picture data and of skipping the B-picture data is used.
In the above-mentioned case, it is desirable to shorten a processing time as far as possible. However, intervals between the I-picture data or the P-picture data are not constant in the MPEG video data because information compressive rates for respective frames are different from each other. As a result, a conventional MPEG data processing apparatus sequentially reads all of the MPEG video data in order to skip the B-picture data even a case where only the I-picture data or the P-picture data are necessitated in the manner which will later become clear.
In addition, various preceding arts related to the present invention are already known. By way of example, UK Patent Publication No. GB 2308264 discloses an MPEG video disk recording system for high-speed reproduction. According to GB 2308264,a disk for high-speed reproduction contains position information of successive I-pictures in a recording area of a present I-picture. Using the above disk, a predetermined waiting time is set in a timer based on a selected multiple speed when moving image data is reproduced at high speed. Referring to the position information of the I-pictures read from the disk, a pickup is moved to the position of the following I-picture to then be reproduced. The data is reproduced at the moved position if the waiting time given by the timer is reached. A larger amount of image information is used within a given time according to each selected multiple speed in order to realize a high-speed reproduction operation with a more natural image displayed.
Japanese Unexamined Patent Publication of Tokkai No. Hei 9-200,695 or JP-A 9-200695 discloses a method and apparatus for decoding video data for high-speed reproduction. According to JP-A 9-200695, picture size items are set in user data in a picture to restrict a coded size of the picture in question. Inasmuch as I-pictures, P-pictures, and B-pictures in MPEG video data are coded in variable length, the coded size of the picture is extremely variable in accordance with complexity of the picture, brightness, and correlation relationship between fore and aft pictures. By doing such as this, although all of data are not searched for a picture start point of a following picture by reading all of data and by comparing picture-start-codes, the coded size of the picture is recognized, it is possible to rapidly shift to the start point of the fore and aft pictures, and it is possible to skip picture data.
Japanese Unexamined Patent Publication of Tokkai No. Hei 10-66,021 or JP-A 10-66021 discloses xe2x80x9cMETHOD FOR RECORDING COMPRESSED PICTURE DATAxe2x80x9d, to effectively execute specific reproduction such as high speed reproduction without increasing the recording data volume by dividing digital compressed picture data into a plurality of areas in accordance with a picture sort, recording the divided data in a recording medium and selectively reproducing data in each area. According to JP-A 10-66021, an area division block divides generated digital compressed picture data into an area including I pictures and an area including P and B pictures and records the divided data in a recording medium through a record processing block. The digital compressed picture data recorded in the medium are read out by a reading processing block, extended by an extending processing block and D/A converted by a D/A conversion circuit and the analog data are outputted as a reproduced signal. In this case, high speed reproduction such as quick feeding, reverse rotation and index reproduction can be attained by continuously reading out only I pictures in one area.
Japanese Unexamined Patent Publication of Tokkai No. Hei 10-42,255 or JP-A 10-42255 discloses xe2x80x9cMOVING PICTURE RECORDING DEVICE, RECORDING MEDIUM AND MOVING PICTURE REPRODUCING DEVICExe2x80x9d to efficiently reproduce only a specified frame by detecting a specified frame from an encoded picture data string and recording the position of the detected frame on a recording medium. According to JP-A 10-42255, a reference frame detection circuit retrieves the position of a header code showing the start of a reference frame arranged in the inputted data string. A table generation circuit generates a reference table indicating a positional relationship in the data string of the reference frame based on the start position of the reference frame which is detected in the reference frame detection circuit. A recording conversion circuit converts an input data string and recording conversion circuit the reference table into forms where they can be recorded in the recording medium. A recording control circuit executes control required for the recording of the recording medium. When reference frame information recorded in the table is referred to and data is skipped and reproduced at the reproduction, high speed reproduction is possible. When data is skipped and reproduced by skipping one piece, the two-fold reproduction of high speed reproduction is possible.
Japanese Patent Publication No. 2773594 or JP-B 2773594 discloses xe2x80x9cMETHOD FOR REPRODUCING FAST FEED PICTURE AND FAST RETURNED PICTURE FROM MOTION PICTURE INFORMATION SUBJECT TO HIGH EFFICIENCY CODINGxe2x80x9d to obtain a reproduced picture with a smooth motion from motion picture information subject to high efficiency coding at the timer of reproduction of fast feed picture and fast returned picture. According to JP-B 2773594, when a picture of only I frame is selected and reproduced from a bit stream in which I, P, B frames or the like are in existence in mixture and a fast feed/fast returned picture is reproduced, the average interval between I mutual frames arranged in the bit stream is arranged so as to be a predetermined interval by which an interval of displayed pictures is made constant, and the retrieval of an I frame to be reproduced succeedingly to the reproduced I frame is started from a position resulting from subtracting a predetermined value K from an integer multiple of the predetermined interval in the case of reproduction of a fast feed picture and the retrieval of an I frame to be reproduced succeedingly to the reproduced I frame is started from a position resulting from adding a predetermined value M to an integer multiple of the predetermined interval in the case of reproduction of a fast returned picture. Thus, a time required to detect an object I frame is reduced, number of reproduced pictures per unit time is increased and a reproduced picture with smooth motion is easily obtained.
Although the above-mentioned publications are related to this invention, each of the above-mentioned publications merely discloses a technical idea which is quite different from this invention. That is, GB 2308264 merely discloses the MPEG video disk for high-speed reproduction which must contain position information of successive I-pictures in a recording area of a present I-picture. In addition, JP-A 9-200695 merely discloses a technical idea in which a picture must store picture size information. Furthermore, JP-A 10-66021 merely discloses a technical idea in which digital compressed picture data are recorded in a recording medium with the digital compressed picture data divided into an area including I pictures and an area including P and B pictures. JP-A 10-42255 merely discloses a technical idea in which information for specifying a position of a reference frame (specified frame) in a picture data string is recorded in a recording medium. In addition, JP-B 2773594 merely discloses a technical idea in which the average interval between I mutual frames arranged in the bit stream is arranged so as to be a predetermined interval by which an interval of displayed pictures is made constant.
It is therefore an object of this invention to provide an MPEG data processing apparatus, which is capable of processing an MPEG video,data at a high-speed.
Other objects of this invention will become clear as the description proceeds.
On describing the gist of an aspect of this invention, it is possible to be understood that a moving picture coding experts group (MPEG) data processing apparatus successively extracts, as extracted picture data, particular picture data from MPEG video data to obtain original picture data from the extracted picture data. According to the above-mentioned aspect of this invention, the above-understood MPEG data processing apparatus comprises a first arrangement for detecting a current particular picture datum in the MPEG video data to obtain a detected result. The first arrangement estimates, as an estimated interval, an interval between the current particular picture datum and a predicted next particular picture datum in accordance with the detected result. Connected to the first arrangement, a second arrangement extracts, as a predicted one of the extracted picture data, the predicted next particular picture datum in accordance with the estimated interval.
On describing the gist of another aspect of this invention, it is possible to be understood that a particular picture searching section searches moving picture coding experts group (MPEG) video data for particular picture data. According to the afore-mentioned aspect of this invention, the above-understood particular picture searching section comprises a first arrangement for detecting a current particular picture datum in the MPEG video data to obtain a detected result. The first arrangement estimates, as an estimated interval, an interval between the current particular picture datum and a predicted next particular picture datum in accordance with said detected result. Connected to the first arrangement, a second arrangement extracts, as a predicted one of the particular picture data, the predicted next particular picture datum in accordance with the estimated interval.
On describing the gist of still another aspect of this invention, it is possible to be understood that a searching method successively searches moving picture coding experts group (MPEG) video data for particular picture data. According to the above-mentioned aspect of this invention, the above-understood method comprises the steps of estimating, as an estimated particular picture interval, a next particular picture interval between a current particular picture datum and a predicted next particular picture datum using a past particular picture interval between the current particular picture datum and a previous particular picture datum, and of extracting the predicted next particular picture datum from the MPEG video data on the basis of the estimated particular picture interval.